Textile yarn cores, i.e., yarn carriers or bobbins, are employed in the textile industry for winding and supporting yarn packages. In the package forming process, a moving yarn line is strung up onto a rapidly rotating empty core. In the manual string-up process, the moving yarn line is usually held by an aspirator gun and the yarn line brought into tangential contact with the rotating empty core. Typically, a start-up groove is provided in the surface of the core, normally adjacent to one end of the core. The yarn line is manually directed by movement of the aspirator gun into the groove which grips the yarn line thereby initiating the wind-up process.
Newer winder technologies provide for the string-up process to be automatically initiated without manual intervention. For example with turret-type winders, an empty yarn core is moved from a waiting position to a winding position when a fully wound yarn package is formed on another position on the apparatus. The empty core is rotated rapidly and moved into tangential contact with the thread line being wound on the other, now full, yarn package. This initiates string-up for the empty core and terminates winding for the fully wound core. For this automated process to work effectively, the start-up groove on the empty core must readily and reliably catch the incoming yarn line without operator intervention.
Multiple width start-up grooves in yarn cores have been provided in an effort to improve the yarn pick up propensities of the yarn groove. In the multiple width pick up grooves, one longitudinal, i.e., lengthwise, portion of the groove is relatively wide while an adjacent longitudinal portion is relatively narrow. The core is rotated so that the wide portion of the groove forms the leading portion; the narrow portion of the groove forms the trailing portion. The transition portion of the groove then forms a "nip" for gripping and catching of the yarn.
A textile core having such a double width groove and the process for forming it are disclosed in U.S. Pat. No. 3,103,305 to Heatherly. The grooves formed according to the disclosure of this patent have a generally V shaped cross-section with the sides of the groove being curved convexly inwardly towards each other. This groove configuration is said to permit the yarn to find its proper maximum position for sliding through the wide, lead-in portion of the groove while acting with maximum efficiency to catch, hold and sever the yarn as it is pulled into the nip while raising to a higher level in the narrow portion of the groove.
Universal pick up grooves for textile cores are disclosed in U.S. Pat. Nos. 4,369,933 to Bedenbaugh and U.S. Pat. No. 4,371,130 to Case. The pick-up grooves described in these patents include wide lead-in portions and adjacent narrow gripping portions. Two wide lead-in longitudinal groove portions are provided, one on each end of the narrow longitudinal portion of the pick-up groove so that the tube can be rotated in either direction while providing the wide, lead-in portion of the groove at the leading edge of the groove. The disclosure of these patents is hereby incorporated herein by reference.
Textile cores having a double taper or compound start-up groove are disclosed in U.S. Pat. No. 3,717,291 to Adams, et al. which is hereby incorporated by reference. The compound angle start-up groove is advantageously formed in the core using a compound angle cutting blade. In transverse cross-section, the compound angle cutting blade is defined by a narrow angle portion at the cutting tip of the blade and a wider angle portion spaced from the cutting tip. The resultant double taper groove in the yarn tube is wider and has a greater angle taper adjacent the surface of the tube, and is narrower, with a narrower taper at the bottom of the groove. A "pinch point" for the incoming yarn line is formed by the narrow tapering portion of the groove at the bottom of the groove.
In practice, the double-taper blades employed in the above-described Adams, et al. patent are typically ground on an abrasive stone-type grinder to achieve the proper tapers. The blade manufacturing process is relatively complicated and time consuming. In addition, care must be exercised during the grinding process in order not to adversely affect the temper of the metal of the grooving blade.
U.S. Pat. No. 5,029,762 to Behrens is directed to a yarn winding apparatus and method and discloses yarn catching slots which are said to be particularly useful in connection with winders wherein the surface of an empty yarn core or tube, and the yarn, move in the same direction at the time when the yarn is strung up on the empty core. In the embodiment illustrated in FIG. 11 of this patent, a portion of the start-up groove is shaped so that each wall includes sawtooth-like projecting radial edges. The radial edges on the opposed walls are displaced relative to each other, i.e. the edges are staggered. The spacing between opposed sawtooth like projecting radial edges is smaller than the yarn thickness and can be zero or negative. An identical start-up groove is disclosed in German Offenlegungsschrift DE 3923305 A1, published Jun. 11, 1990. As shown in FIGS. 8A and 8B thereof and described in the specification thereof, the edges of the sawtooth-like projections are said to form tongues projecting into the axial center of the catch-thread slot to act as thread traps. The groove was said to be made by punching a suitable tool into the surface of the yarn tube. A related start-up groove is illustrated in FIGS. 7A and 7B of this publication which is formed by first punching a series of circumferentially arranged holes into the surface of the tube and thereafter cutting into the surface of the tube a slot intersecting the previously formed holes. A further related start-up groove is shown in FIGS. 6 and 6A wherein notches are made in the surface of the tube transverse to the catch-thread slot. The notches are said to give rise to paper tongues for forming a trap for engaging an incoming thread line.
The yarn start-up grooves disclosed in the above described German patent publication and in the Behrens, et al. patent, are said to be formed in paperboard textile cores by pressing one or more appropriately shaped tools into the surface of the core. However, in practice, irregularly shaped start-up grooves, such as those described above, tend to loose their shape because the slot is impressed into the paperboard core and no material is removed from the core during the slot-forming process. As a result the slot is defined by compressed paperboard areas adjacent the slot. Over time, these compressed areas adjacent the groove tend to expand due to the tendency of the paperboard material to spring back into its original shape as a result of moisture regain and the natural resiliency of the paperboard fibers. Moreover, the compound shaped grooves described above can require the use of specially shaped cutting blades which are difficult to form in practice and/or multiple cutting operations are required using multiple tools in order to form the start-up grooves. In addition to the difficulties in forming the grooves, and/or the cutting tools used to form the grooves, it has been found in practice that notched grooves, such as those shown in FIGS. 6A and 6B of the above German patent publication can be difficult to use reliably, particularly in high speed winding processes employing automated string-up turret-type winders, and when used for high denier yarns, such as continuous, multifilament industrial yarns.
In the textile industry, yarn manufacturing and wind-up speeds have continually increased. Moreover, in many cases, yarn properties including yarn strengths have increased. As yarn manufacturing speeds have increased, the need for improved gripping action by the start-up groove in the textile cores has also increased. Moreover, in the case of automated string-up winders, the gripping action of the start-up groove must be extremely reliable so that the yarn line can be readily gripped and severed without operator intervention. However, it has been found that conventionally formed start-up grooves in textile yarn cores do not always reliably and repeatably perform these functions, particularly when used with different sized yarns, yarns of different strengths and/or with automated winding apparatus of high speeds.
Because of these and other difficulties associated with start-up grooves in textile cores, there are in excess of 100 different groove configurations in use commercially. In general, the grooves are V-shaped and can vary by having both sidewalls tapered, or only a single wall tapered, and/or the angle of taper on the sidewall or sidewalls can be varied. In addition, the entire groove can be formed at an angle with respect to the peripheral surface of the textile core, either in the "outboard" direction (i.e. the groove is slanted toward the direction of the end of the textile core) or in the "inboard" direction (rotation in the direction of the middle of the textile core). Such widely varying groove shapes and configurations are necessary due to varying yarn deniers and strengths and due to variations in operations of commercially available winding apparatus. Moreover, the compound shaped and notched grooves described above add further start-up groove specifications to those commercially available. The manufacture and stocking of textile cores having such numerous groove configurations decreases manufacturing efficiencies and increases manufacturing costs for the textile core manufacturing industry.